Clock Tree Fault Detection with Flip-Flop Pattern Monitoring
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Solution Overview
Problem
Existing digital electronic circuitry, particularly clock tree circuitry, is vulnerable to fault attacks that cause abnormalities in clock signals, making it difficult to detect and protect against such attacks effectively.
Innovation Solution
The integration of protection circuitry within the IC that samples multiple instances of the clock signal at various points and uses a cascade of Flip-Flop stages to detect deviations from a predetermined alternating pattern, triggering an alert or action upon fault detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If protection circuitry is added to detect faults in clock tree circuitry, then security against fault attacks is improved, but device complexity increases
Solution Approach 1:
The protection circuitry is merged with the existing clock tree circuitry by using the same clock signal distribution paths. The Flip-Flop cascade is integrated into the clock tree structure, sampling clock signals at multiple points along the existing distribution network, thereby detecting faults without adding separate monitoring infrastructure.
Solution Approach 2:
The clock tree circuitry serves dual purposes: it distributes clock signals to functional units and simultaneously provides sampling points for fault detection. The existing clock signal paths self-generate the test samples needed for fault detection, eliminating the need for external test equipment or separate monitoring circuits.
2Measurement precision
If multiple sampling points are used to detect clock signal abnormalities, then fault detection capability is improved, but device complexity increases
Solution Approach 1:
The clock tree distribution network is segmented into multiple sampling zones, with Flip-Flops placed at different hierarchical levels (root, intermediate, and leaf nodes). Each sampling point monitors a specific segment of the clock tree, enabling localized fault detection without requiring comprehensive monitoring of the entire system at once.
Solution Approach 2:
The Flip-Flop elements serve dual functions: they sample clock signals for fault detection and simultaneously act as functional units that receive clocking for their operations. This multi-functionality reduces the need for dedicated monitoring components, thereby limiting the increase in device complexity.
3Measurement precision
If a cascade of Flip-Flop stages is used to detect deviations from alternating pattern, then fault detection accuracy is improved, but device complexity increases
Solution Approach 1:
The Flip-Flop cascade is configured to generate and detect alternating patterns (101010...) at its output. This periodic action creates a predictable reference signal that is easy to monitor for deviations. The alternating pattern emerges naturally from the sequential toggling of Flip-Flops clocked by the clock tree signals, requiring no additional pattern generation circuitry.
Solution Approach 2:
The detector monitors the output of the Flip-Flop cascade and compares it against the expected alternating pattern. When a deviation is detected, it indicates a fault in the clock tree circuitry. This feedback mechanism provides continuous verification of clock signal integrity without requiring complex analysis, as the alternating pattern creates a simple binary comparison scenario.
Data Source
AI summary
An Integrated Circuit (IC) includes clock-tree circuitry and protection circuitry. The clock-tree circuitry is configured to distribute a clock signal across the IC. The protection circuitry is clocked by multiple instances of the clock signal that are sampled at multiple sampling points in the clock-tree circuitry, and is configured to detect a fault in the clock-tree circuitry in response to an abnormality in one or more of the instances of the clock signal.